1. Field of the Invention
The present invention relates to a regenerative braking system in a motor vehicle, particularly a regenerative braking system in a motor vehicle for performing a regenerative braking in accordance with a state of deceleration which has been judged on the basis of the number of revolutions of a motor and an accelerator signal. In addition, the present invention is directed to a power unit suitable for providing power thereto.
2. Description of Background Art
In a motor vehicle, as is well known, electric power is supplied from a battery to a vehicle driving motor mounted on the vehicle, thereby imparting movement to the vehicle. In such a motor vehicle, when the vehicle is to be braked, a regenerative braking is performed and the kinetic energy of the vehicle is recovered as electric power to charge the battery.
On the other hand, for imparting a function corresponding to an engine brake to an automobile using an internal combustion engine, there has been proposed a method (Japanese Patent Publication No. 12446/77) in which, when the accelerator signal level decreases, a differential value thereof is taken and switching is made into a regenerative braking state during a period corresponding to the said differential value, thereby maintaining the motor vehicle in a braked condition during that period.
In addition, a motor vehicle is also well known, wherein an output of an electric motor serves as a power source which is transmitted to a wheel to drive the wheel, thereby causing the vehicle to impart motion thereto. Motor vehicles of this type are known as described in Japanese Patent Laid Open No. 38043/79 and Utility Model Laid Open No. 80848/76.
In the above motor vehicles, particularly motor-driven two-wheeled vehicles, it is absolutely necessary to provide a power unit which is a combination of an electric motor and a power transmission mechanism. The present inventors have also proposed a power unit for motor vehicles suitable for two-wheeled vehicles as set forth in Japanese Patent Application No. 181496/89, filed in the Japanese Patent Office on Jul. 13, 1989.
According to the construction of the power unit for motor vehicles as previously set forth, a power transmission mechanism such as a stepless transmission is enclosed in a unit case, and a motor case of an electric motor is connected to the unit case using bolts or the like. A rotating shaft of the electric motor is connected to the stepless transmission. Further, a drive circuit connected by wiring to the electric motor is provided in the vehicle body for example to supply electric power to the motor.